Ashley Merritt packs an order for shipping at the Amazon fulfillment center in Lebanon, Tenn. on Monday, Dec. 1, 2014. Retailers rolled out discounts and free shipping deals on Cyber Monday, with millions of Americans expected to log on and shop on their work computers, laptops and tablets after the busy holiday shopping weekend. (AP Photo/Mark Humphrey)

Ashley Merritt packs an order for shipping at the Amazon fulfillment center in Lebanon, Tenn. on Monday, Dec. 1, 2014. Retailers rolled out discounts and free shipping deals on Cyber Monday, with millions of

Retailers rolled out discounts and free shipping deals on Cyber Monday, with millions of Americans expected to log on and shop on their work computers, laptops and tablets after the busy holiday shopping weekend.

But with retailers extending their online deals into "Cyber Week" and even "Cyber Month," early reports indicated shopping was less robust online on Monday compared with prior years. As of 3 p.m. ET, online sales rose just 8.7 percent compared with last year, according to IBM Digital Analytics. The figures don't take into account the many shoppers who plan to head online after work or in the evening. But a year ago, Cyber Monday sales jumped 20.6 percent, according to IBM.

It is still expected to be the biggest online shopping day again, as it has been each year since 2010. That is good news for retailers after a Thanksgiving weekend that saw fewer shoppers and lower spending than last year, according to some estimates. Mobile traffic, which includes smartphones and tablets, has accounted for nearly 39 percent of all online traffic, compared with 30 percent a year ago. Average order value was $133.07, flat with 2013. Forrester analyst Sucharita Mulpuru said retailers could be playing it safe on deal offers since shoppers have been conditioned to head online to look for sales on Monday.

"Cyber Monday offers aren't super compelling, but don't need to be," she said. "It's been the biggest shopping day of the year for the last few years, so they know that people are going to come."

This Cyber Monday comes after a weekend that saw 5.3 percent fewer shoppers and 11 percent less spending, according to estimates by the National Retail Federation. Research firm comScore said that e-commerce spending for the first 28 days of the November and December shopping season totaled $22.7 billion, up 15 percent from last year.

Sales jumped 32 percent to $1 billion on Thanksgiving Day and 26 percent on Black Friday to $1.51 billion. The firm expects people to spend about $2.5 billion on Cyber Monday alone.

The NRF predicts 126.9 million people will shop online this year, down 4 percent from last year. It has forecast overall holiday sales will increase 4.1 percent to $616.9 billion in 2014.

In Asia and Europe, Black Friday and Cyber Monday have increasingly been used as marketing ploys by retailers, even though Thanksgiving isn't celebrated. In Asia, Singles Day, which occurs on Nov. 11, still is by far the biggest shopping day, with sales of $9.3 billion this year. That's bigger than U.S. sales of Thanksgiving through Cyber Monday combined.